FIRE SAFETY

Redefining Smoke

UL scientists have identified the composition of today's smoke and its higher levels of toxicity. UL is working to understand the long-term health risks to firefighters from exposure to smoke particles in modern home and office fires.

CONTEXT

The new synthetic materials frequently used in residential buildings, furniture, electronic appliances and even toys have changed the nature of fire and of smoke as well. UL has been studying how materials have evolved over the past 30 years and how smoke chemistry has been affected by the changes in material properties. UL’s New Science demonstrates the potential effects of the changes in smoke chemistry on materials science, fire behavior, smoke detection technology and firefighter safety.

WHAT DID UL DO?

Researchers at UL have been actively engaged in ongoing investigations regarding the changing nature of modern fires, the effectiveness of current smoke detection technologies and the implications of today’s smoke on firefighter safety.

The shift from natural to synthetic materials in modern homes has created an environment where fires develop much faster and move more rapidly to untenable conditions. As such, the amount of time available to safely escape from a fire is much shorter than it was in the past, placing a greater burden on smoke alarms to respond at the earliest possible stages of a fire. In fact, a percentage of smoke alarms react faster to the type of smoke released by these new modern materials, which is different in composition from the smoke generated by natural materials.2

In response to data relating to smoke characteristics of modern materials, UL is working with other safety professionals and manufacturers to develop new methods and data to further promote innovation of new smoke detection technologies.3

In addition to new detection challenges caused by the chemistry of new materials, the type and quantity of smoke particles generated when synthetic materials are ignited are also characteristically different from those of natural materials. One of the key observations noted in the landmark UL-FPRF Smoke Characterization Project was the predominance of submicron-sized smoke particles generated by combustion. Working with the NFPA Fire Protection Research Foundation (FPRF) and the smoke detector industry, the complex research investigation sought to answer the basic question: What is smoke? Beyond this foundational research, UL further investigated the causal relationship between submicron smoke particles and the risk of cardiovascular problems. UL partnered with the Chicago Fire Department and the University of Cincinnati College of Medicine to collect data on the smoke and gas effluents to which firefighters are exposed during routine firefighting operations, as well as contact exposure from contaminated personal protective equipment. This research was funded by a substantial grant from the U.S. Department of Homeland Security.4

As a component of this study, the combustibility, smoke and gas characteristics of 42 different residential construction and furnishing materials were characterized using the methodology developed in the UL-FPRF Smoke Characterization Project. This increased the number of measured smoke signatures from 18 materials, originally completed in the UL-FPRF Smoke Characterization Project, to 60 smoke signatures now currently identified.5

UL’s unprecedented research found definitively that synthetic materials produce more smoke than do natural materials; the combustion of the materials generates asphyxiants, irritants and airborne carcinogenic by-products that could be potentially debilitating; carcinogenic chemicals may act topically, following inhalation or dermal absorption, including from contaminated equipment; and long-term repeated exposure may accelerate cardiovascular mortality and the initiation and/or progression of atherosclerosis.6

UL’s research found that synthetic materials produced more smoke than natural materials and thatthe combustion of the synthetics generated asphyxiants, irritants and airborne carcinogenic by-products.

UL research scientists and engineers also determined that flaming and nonflaming polyurethane foam produce smoke with characteristics that are different from those used to evaluate smoke alarms under UL 217. Accordingly, UL formed a task group under the UL 217 Standards Technical Panel (STP) to develop tests for flaming and nonflaming polyurethane foam. The objective of the task group was to expand the number of smoke signatures to which smoke alarms are evaluated under the standard. To date, the task group has established target performance criteria for the new fire tests that will not inadvertently cause an increase in nuisance-alarm frequency. UL has also investigated the smoke produced by samples of commercially available foams used in mattresses and upholstered furniture, covering a range of densities.7

In addition, the task group has investigated how sample size, geometry, density, mode of combustion and mode of heating impact smoke particle size, count distribution and smoke concentration buildup rates. In the final stages of its work, the task group is using its results to select the test foam material and the flaming and smoldering test protocols to be proposed to the UL 217 STP. Test material specifications and test consistency limits are now being formulated for the selected test protocols generated by the task group.8

One unanticipated issue in the development of material specifications and test consistency limits has been the discovery that the cell size of polyurethane foam (independent of the foam density) significantly impacts the smoke buildup rate, particularly for the slower, smoldering fire test protocol. To further investigate this issue, the task group is currently pursuing two approaches: developing test material specifications and test consistency limits for a range of commercially available foams that meet the test material property targets, and developing a standard reference for polyurethane foam.9

Once the material properties (chemistry, density, indentation load density, cell size, etc.) have been determined, the proposed test protocols will be statistically repeatable to establish the test consistency limits, and the task group will submit the developed test protocols (including test sample specifications) to the UL 217 STP for review and consideration.

UL will pursue in-depth analysis of existing studies of firefighter cancer epidemiologies and the character- ization of both potential fire scene exposure to toxic chemicals and contaminants accumulated on firefighter protective equipment.

WHY IT MATTERS

The changing nature of smoke creates significant health risks for both home occupants and firefighters. For home occupants, it is imperative that smoke detection technologies be effective so people have sufficient time to escape a burning home. For firefighters, early detection gives them more time to effectively fight fires at the earliest possible stage. Understanding the health risks to firefighters from long-term exposure to today’s more toxic smoke particles is also important so that successful countermeasures can be developed.

IMPACT

As UL’s continuing research is made available, the results can lead to advancements in products, product safety standards, model codes and regulations. The ultimate goal of UL’s smoke alarm research is to provide the technological data that can help reduce and/or eliminate fire deaths.10

UL is pursuing additional research that builds on the Firefighter Exposure to Smoke Particulates investigation to advance the unique findings to date. UL will pursue in-depth analysis of existing studies of firefighter cancer epidemiologies and the characterization of both potential fire scene exposure to toxic chemicals and contaminants accumulated on firefighter protective equipment. We will work in conjunction with leading organizations and universities to develop a better definition of the potential long-term respiratory, cancer and cardiovascular health impacts and determine the relative contribution of respiratory and dermal absorption routes of exposure. Last, our research, working cooperatively with key partners and associations, will examine the usage of and industrial hygiene practices related to firefighter protective equipment.

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